Advanced Diagnostics

Advanced Diagnostics - DTC P0139: Secondary Heated Oxygen Sensor (Secondary HO2S (Sensor 2)) Slow Response (Engine Type: K20Z3)











General Description
The secondary heated oxygen sensor (secondary HO2S (sensor 2)) detects the oxygen content in the exhaust gas downstream of the three way catalytic converter (TWC) during stoichiometric air/fuel ratio feedback control. The engine control module (ECM) controls the air/fuel ratio with the air/fuel ratio (A/F) sensor (sensor 1) output voltage to optimize the TWC's efficiency. If the response time of the secondary HO2S becomes longer than the specified time after current to the secondary HO2S heater is applied, the ECM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
1. When the secondary HO2S output drops to the response deterioration judgment threshold value and the response characteristics measurement is finished.






2. The voltage does not drop to the response deterioration judgment threshold value after a predetermined time (1.0 second) has elapsed.

Driving Pattern
1. Start the engine, and let it idle until the radiator fan comes on.
2. Drive immediately at a steady speed of 30 mph (48 km/h) or more for at least 12 seconds.

- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the ECM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.